$\forall$$A$:Type, ${\it eq}$:EqDecider($A$), $f$, $g$:$a$:$A$ fp$\rightarrow$ Top, $x$:$A$, $z$:Top. $f$ $\oplus$ $g$($x$)?$z$ $\sim$ $f$($x$)?$g$($x$)?$z$